Driver module structure

ABSTRACT

A driver module structure includes a flexible circuit board ( 2 ) provided with a wiring pattern ( 7 ), a semiconductor device mounted on the flexible circuit board ( 2 ), and an electrically conductive heat-radiating member ( 4 ) joined to the semiconductor device. The wiring pattern ( 7 ) includes a ground wiring pattern ( 8 ). The flexible circuit board ( 2 ) has a cavity ( 9 ) that exposes a portion of the ground wiring pattern ( 8 ). The exposed portion of the ground wiring pattern ( 8 ) and the heat-radiating member ( 4 ) are connected to establish electrical continuity via a member ( 11 ) that is fitted into the cavity ( 9 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of application Ser. No. 10/598,903,filed Sep. 14, 2006, now U.S. Pat. No. 7,582,959 issued on Sep. 1, 2009,which is a U.S. National Stage of PCT/JP2005/004349, filed Mar. 11,2005, which applications are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a driver module structure of a TCP(tape carrier package) used for a flat display or the like.

BACKGROUND ART

FIG. 9 is a perspective view of an example of a conventional drivermodule structure and shows the main part of the driver module structure.The driver module structure of FIG. 9 is an example in which a largeamount of heat is generated from a semiconductor device that controls aflat display or the like (see, e.g., Patent Document 1).

In FIG. 9, a driver module 30 includes a flexible circuit board 31provided with a wiring pattern, semiconductor devices 32 connected tothe flexible circuit board 31, and a heat-radiating member 34. In thisconfiguration, the heat-radiating member 34 is joined to the back (upperportion) of each of the semiconductor devices 32. Thus, the heatgenerated from the semiconductor devices 32 is radiated into thesurroundings via the heat-radiating member 34, and the semiconductordevices 32 are cooled.

For the conventional driver module structure of FIG. 9, theheat-radiating member 34 may be connected to a ground to suppress theeffect of electromagnetic interference (EMI) on the semiconductordevices 32. In such a case, one end of a ground wire is connected to theheat-radiating member 34 with screws or the like and the other end isconnected to a case that is a ground of an apparatus incorporating thedriver module or a ground of the substrate, so that the heat-radiatingmember 34 can be shielded.

However, when the ground wire is used to connect the heat-radiatingmember 34 and the ground, the length of the ground wire becomes long.This increases the impedance for higher harmonics and reduces the effectof suppressing the EMI. Moreover, the ground wire itself may act as anantenna and generate harmonics.

Patent Document 1: JP 2000-299416 A

DISCLOSURE OF INVENTION

The present invention solves the above conventional problems and has anobject of providing a driver module structure that can improve the EMIsuppression effect with a simple structure while maintaining the heatradiation effect of a heat-radiating member.

To achieve the object, a driver module structure of the presentinvention includes a flexible circuit board provided with a wiringpattern, a semiconductor device mounted on the flexible circuit board,and an electrically conductive heat-radiating member joined to thesemiconductor device. The wiring pattern includes a ground wiringpattern. The flexible circuit board has a cavity that exposes a portionof the ground wiring pattern. The exposed portion of the ground wiringpattern and the heat-radiating member are connected to establishelectrical continuity via a member that is fitted into the cavity.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a driver module structure in Embodiment1 of the present invention.

FIG. 2 is a perspective view of a heat-radiating member of the drivermodule structure in Embodiment 1 of the present invention.

FIG. 3 is a cross-sectional view showing a main part of the drivermodule structure in Embodiment 1 of the present invention.

FIG. 4 is a perspective view of a driver module structure in Embodiment2 of the present invention.

FIG. 5 is a cross-sectional view showing a main part of the drivermodule structure in Embodiment 2 of the present invention.

FIG. 6 is a cross-sectional view showing a main part of a driver modulestructure in Embodiment 3 of the present invention.

FIG. 7 is a cross-sectional view showing a main part of a driver modulestructure in Embodiment 4 of the present invention.

FIG. 8 is a cross-sectional view showing a main part of a driver modulestructure in Embodiment 5 of the present invention.

FIG. 9 is a perspective view of an example of a conventional drivermodule structure.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention can achieve a driver module structure thatimproves the shielding effect with a simple structure while maintainingthe heat radiation effect.

In the driver module structure of the present invention, it ispreferable that the cavity is a recess for exposing a portion of theground wiring pattern to the heat-radiating member, and the memberfitted into the cavity is a projection of the heat-radiating member.This configuration can connect the heat-radiating member to the groundat the shortest distance.

It is preferable that the exposed portion of the ground wiring patternand the projection are connected via an electrically conductive bondingmaterial. This configuration can improve both the bond strength andelectrical conductivity.

It is preferable that the cavity is a through hole penetrating theground wiring pattern, a portion of the ground wiring pattern on theopposite side from the heat-radiating member is exposed, and the memberfitted into the cavity is a projection of the heat-radiating member.This configuration can connect the heat-radiating member to the groundat the short distance and further relax the required accuracy of theheight of the projection.

It is preferable that the projection is hollow, and the end of theprojection is deformed so that the exposed portion of the ground wiringpattern and the projection are connected to establish electricalcontinuity. This configuration can improve the bond strength by theheat-radiating member itself without using any other dedicated fasteningmeans.

It is preferable that the exposed portion of the ground wiring patternand the projection are connected via an electrically conductive bondingmaterial. This configuration can improve both the bond strength andelectrical conductivity.

It is preferable that the cavity is a through hole penetrating theground wiring pattern, a portion of the ground wiring pattern on theopposite side from the heat-radiating member is exposed, and the memberfitted into the cavity is a fastener for fastening the flexible circuitboard and the heat-radiating member. This configuration can connect theheat-radiating member to the ground at a short distance and improve thebond strength.

It is preferable that the exposed portion of the ground wiring patternand the fastener are connected via an electrically conductive bondingmaterial. This configuration can improve both the bond strength andelectrical conductivity.

Hereinafter, embodiments of the present invention will be described withreference to the drawings.

Embodiment 1

A driver module structure of Embodiment 1 of the present invention willbe described by referring to FIGS. 1 to 3. Embodiment 1 is an example ofa liquid crystal driver, which also is applied to the followingembodiments. FIG. 1 is a perspective view of the driver module structureof Embodiment 1. FIG. 2 is a perspective view of a heat-radiating memberof the driver module structure of Embodiment 1. FIG. 3 is across-sectional view taken along the line AA′ in FIG. 1 and shows astate in which a recess of a flexible circuit board and a projection ofthe heat-radiating member are fitted together.

As shown in FIG. 1, a driver module 1 includes a flexible circuit board2, a semiconductor device 3 mounted on the flexible circuit board 2, anda heat-radiating member 4 joined to the flexible circuit board 2 and thesemiconductor device 3. The flexible circuit board 2 is made of aflexible plastic film. An electrode 5 connected to a liquid crystalpanel is formed at one end of the flexible circuit board 2, and anelectrode 6 connected to a control substrate (not shown) is formed atthe other end. The electrodes 5, 6 and the semiconductor device 3 areconnected by a wiring pattern 7.

The electrode 5 of the flexible circuit board 2 is connected to atransparent electrode formed on the liquid crystal panel via ananisotropic conductive film (ACF) or anisotropic conductive paste (ACP).The electrode 6 of the flexible circuit board 2 is connected to anelectrode formed on the control substrate by soldering or the like. Thewiring pattern 7 of the flexible circuit board 2 includes a ground line8 as a reference potential of the semiconductor device 3, a power line(not shown) for applying a voltage, and various types of signal lines(not shown).

The semiconductor device 3 is an IC that performs display control of theliquid crystal panel. The semiconductor device 3 is connected to thewiring pattern 7 of the flexible circuit board 2 by metal bonding and issealed with resin.

As shown in FIG. 2, the heat-radiating member 4 is substantiallyrectangular in shape when viewed from above. There is an accommodatingportion 10 in the center of the heat-radiating member 4 foraccommodating the semiconductor device 3. The heat-radiating member 4 isattached to the semiconductor device 3 and the flexible circuit board 2with a heat radiation agent that is applied to the inner sides of theaccommodating portion 10 and the surface that comes into contact withthe flexible circuit board 2. For attachment, the heat-radiating member4 either may be fixed completely by bonding or provided movably viagrease or the like. A projection 11 is fitted into a recess 9 formed inthe flexible circuit board 2, which will be described in detail later byreferring to FIG. 3.

The heat-radiating member 4 preferably is made of a material whosethermal conductivity is as high as possible to improve the heatradiation effect. Moreover, the heat-radiating member 4 should haveelectrical conductivity for connection to the ground line 8. Forexample, Al is suitable for the material of the heat-radiating member 4because it meets those requirements and also is lightweight.

Next, the state in which the recess 9 of the flexible circuit board 2and the projection 11 of the heat-radiating member 4 are fitted togetherwill be described in detail by referring to FIG. 3. As shown in FIG. 3,the flexible circuit board 2 is formed by sandwiching the wiring pattern7 (ground line 8) between an upper cover 12 and a lower cover 13.

The upper cover 12 has a thickness of, e.g., 15 μm. The lower cover 13has a thickness of, e.g., 75 μm. The wiring pattern 7 is made of Cu witha thickness of, e.g., 25 μm. In such a three-layer structure, a cavityis formed in part of the lower cover 13 (bottom layer) so as to exposethe ground line 8 of the wiring pattern 7 (intermediate layer). That is,when the flexible circuit board 2 is seen as the whole of three layers,the cavity of the lower cover 13 corresponds to the recess 9.

In the example of FIGS. 2 and 3, the projection 11 is cylindrical inshape. The diameter of the projection 11 is smaller than that of therecess 9 so that the projection 11 is fitted into the recess 9. Byfitting the projection 11 into the recess 9, the heat-radiating member 4functions as a shield for the semiconductor device 3. This configurationcan connect the heat-radiating member 4 to the ground line 8 at theshortest distance and thus improve the EMI suppression effect with asimple structure.

Although the projection 11 is in the form of a cylinder in thisembodiment, it may be a rectangular parallelepiped. Alternatively, theprojection 11 may have different horizontal sections in each part.However, a cylindrical shape is desirable, since the projection 11 canbe fitted easily during manufacture.

When the recess 9 of the flexible circuit board 2 and the projection 11of the heat-radiating member 4 are fitted together, an electricallyconductive thermosetting bonding material such as ACF or ACP may beprovided between the recess 9 and the projection 11, thereby furtherimproving both the bond strength and electrical conductivity. Thebonding material is not limited to ACF or ACP, and any material can beused as long as it has electrical conductivity and joins the projection11 to the recess 9 in which the ground line 8 is exposed. For example,the bonding material may be solder.

It is desirable that the height of the projection 11 of theheat-radiating member 4 is approximately the same as the thickness ofthe lower cover 13. However, even if the height of the projection 11 isabout several μm smaller than the thickness of the lower cover 13, theheat-radiating member 4 can be connected to the ground line 8 when ACFor ACP is used to fit the recess 9 and the projection 11 together. Thisis because the bonding material (ACF or ACP) present between theprojection 11 and the exposed portion of the ground line 8 is cured tojoin them.

Moreover, even if the height of the projection 11 is about several μmlarger than the thickness of the lower cover 13, the heat-radiatingmember 4 can be connected to the flexible circuit board 2. This isbecause the flexible circuit board 2 is made of a flexible plastic film,and excess height of the projection 11 is absorbed by deformation of theupper cover 12. Accordingly, strict accuracy is not required for theheight of the projection 11, and the projection 11 can be processedeasily.

Embodiment 2

A driver module structure of Embodiment 2 of the present invention willbe described by referring to FIGS. 4 and 5. In FIGS. 4 and 5, the samecomponents as those in FIGS. 1 to 3 are denoted by the same referencenumerals, and the explanation will not be repeated.

FIG. 4 is a perspective view of the driver module structure ofEmbodiment 2. As shown in FIG. 4, a driver module 20 includes theflexible circuit board 2, and a through hole 21 penetrating the groundline 8 of the wiring pattern 7 is formed in the flexible circuit board2.

FIG. 5 is a cross-sectional view taken along the line BB′ in FIG. 4 andshows details in the vicinity of the through hole 21. The through hole21 penetrates the upper cover 12, the lower cover 13, and the groundline 8. The diameter of the through hole 21 at the lower cover 13 andthe ground line 8 is large enough to fit the projection 11 of theheat-radiating member 4. Moreover, the diameter of the through hole 21at the upper cover 12 is larger than that at the lower cover 13 and theground line 8. Therefore, a portion of the ground line 8 on the sameside as the upper cover 12 is exposed.

In this configuration, the projection 11 and the through hole 21 arefitted while the projection 11 is inserted through the through hole 21.The end of the projection 11 is connected to the exposed portion of theground line 8 via a bonding material such as ACF or ACP.

It is desirable that the height of the projection 11 is larger than thesum of the thicknesses of the upper cover 12, the lower cover 13, andthe ground line 8. However, the accuracy of the height of the projection11 is not defined strictly, and if the height of the projection 11 is atleast the same as the thickness of the lower cover 13, then theheat-radiating member 4 and the ground line 8 can be connected via ACFor ACP.

In this embodiment, the cavity that connects the projection 11 and theground line 8 is not a recess but a through hole. Thus, the accuracy ofthe height of the projection 11 becomes less strict compared toEmbodiment 1.

Embodiment 3

A driver module structure of Embodiment 3 of the present invention willbe described by referring to FIG. 6. In FIG. 6, the same components asthose in FIG. 5 are denoted by the same reference numerals, and theexplanation will not be repeated. A perspective view of the drivermodule structure in Embodiment 3 is the same as FIG. 4 in Embodiment 2.FIG. 6 is a cross-sectional view taken along the line BB′ in FIG. 4 andshows the main part of the driver module structure in this embodiment.

As shown in FIG. 6, the through hole 21 is formed in the flexiblecircuit board 2, and a through hole 22 is formed in the heat-radiatingmember 4 at the position that is to be aligned with the through hole 21.A rivet (fastening means) 23 is inserted through these through holes 21,22. The rivet 23 connects the flexible circuit board 2 and theheat-radiating member 4.

The rivet 23 has electrical conductivity and comes into contact with theexposed portion of the ground line 8 and the heat-radiating member 4,thereby establishing electrical continuity between the ground line 8 andthe heat-radiating member 4. It is desirable that an electricallyconductive bonding material such as ACF, ACP, or solder is provided onthe contact surfaces of the rivet 23 with the exposed portion of theground line 8 and the heat-radiating member 4.

Embodiment 4

A driver module structure of Embodiment 4 of the present invention willbe described by referring to FIG. 7. In FIG. 7, the same components asthose in FIG. 6 are denoted by the same reference numerals, and theexplanation will not be repeated. A perspective view of the drivermodule structure in Embodiment 4 is the same as FIG. 4 in Embodiment 2.FIG. 7 is a cross-sectional view taken along the line BB′ in FIG. 4 andshows the main part of the driver module structure in this embodiment.

As shown in FIG. 7, the through hole 21 is formed in the flexiblecircuit board 2, and a through hole 24 is formed in the heat-radiatingmember 4 at the position that is to be aligned with the through hole 21.A screw (fastening means) 25 is threadedly fitted to the through hole 24via the through hole 21. The screw 25 fastens and connects the flexiblecircuit board 2 and the heat-radiating member 4.

The screw 25 has electrical conductivity and comes into contact with theexposed portion of the ground line 8 and the heat-radiating member 4,thereby establishing electrical continuity between the ground line 8 andthe heat-radiating member 4. It is desirable that an electricallyconductive bonding material such as ACF, ACP, or solder is provided onthe contact surfaces of the screw 25 with the exposed portion of theground line 8 and the heat-radiating member 4.

The through hole 24 as shown in FIG. 7 is not limited to a through holeand may be a closed cavity.

Although the configurations of Embodiments 3 and 4 require a fastener inaddition to the heat-radiating member 4, they are more advantageous inbond strength than the configurations of Embodiments 1 and 2.

Embodiment 5

A driver module structure of Embodiment 5 of the present invention willbe described by referring to FIG. 8. In FIG. 8, the same components asthose in FIG. 5 are denoted by the same reference numerals, and theexplanation will not be repeated. A perspective view of the drivermodule structure in Embodiment 5 is the same as FIG. 4 in Embodiment 2.FIG. 8 is a cross-sectional view taken along the line BB′ in FIG. 4 andshows the main part of the driver module structure in this embodiment.

As shown in FIG. 8, the heat-radiating member 4 has a hollow projection26. The projection 26 and the through hole 21 are fitted while theprojection 26 is inserted through the through hole 21. Since theprojection 26 is hollow, the end of the projection 26 can be deformedeasily by applying pressure. In FIG. 8, the end of the projection 26 isextended in the radial direction, bent downward, and comes into contactwith the exposed portion of the ground line 8.

This embodiment can ensure that the heat-radiating member 4 is connectedby itself to the flexible circuit board 2 without using any otherdedicated fastening means. The end of the projection 26 may be connectedto the exposed portion of the ground line 8 via a bonding material suchas ACF or ACP.

Each of the embodiments has been described above. The distance ofconnecting the heat-radiating member 4 and the ground line 8 is slightlylonger in the configurations of Embodiments 2 to 5 than in theconfiguration of Embodiment 1. However, there is no difference among theembodiments in terms of making the connection at the shortest possibledistance with a simple structure. Thus, all the configurations can notonly improve the EMI suppression effect with a simple structure, butalso exhibit an excellent shielding effect while maintaining the heatradiation effect of the heat-radiating member.

INDUSTRIAL APPLICABILITY

The present invention can improve the shielding effect while maintainingthe heat radiation effect of a heat-radiating member, and therefore issuitable for a driver module of a TCP used for a flat display or thelike.

1. A driver module structure comprising: a flexible circuit boardprovided with a wiring pattern; a semiconductor device mounted on theflexible circuit board; and an electrically conductive heat-radiatingmember joined to the semiconductor device, wherein the wiring patterncomprises a ground wiring pattern, the flexible circuit board has acavity that exposes a portion of the ground wiring pattern, the exposedportion of the ground wiring pattern and the heat-radiating member areconnected to establish electrical continuity via a member that is fittedinto the cavity, an open portion in which the semiconductor device isnot covered with the flexible circuit board is provided at a positionwhere the semiconductor device is located, the open portion is anopening formed in the flexible circuit board, an accommodating portionfor accommodating the semiconductor device is provided in theheat-radiating member at a position corresponding to the open portion,and the heat-radiating member is attached to the semiconductor devicewith a heat radiation agent.
 2. The driver module structure according toclaim 1, wherein the cavity is a recess for exposing a portion of theground wiring pattern to the heat-radiating member, and the memberfitted into the cavity is a projection of the heat-radiating member. 3.The driver module structure according to claim 2, wherein the exposedportion of the ground wiring pattern and the projection are connectedvia an electrically conductive bonding material.
 4. The driver modulestructure according to claim 1, wherein the cavity is a through holepenetrating the ground wiring pattern, a portion of the ground wiringpattern on an opposite side from the heat-radiating member is exposed,and the member fitted into the cavity is a projection of theheat-radiating member.
 5. The driver module structure according to claim4, wherein the projection is hollow, and an end of the projection isdeformed so that the exposed portion of the ground wiring pattern andthe projection are connected to establish electrical continuity.
 6. Thedriver module structure according to claim 4, wherein the exposedportion of the ground wiring pattern and the projection are connectedvia an electrically conductive bonding material.
 7. The driver modulestructure according to claim 1, wherein the cavity is a through holepenetrating the ground wiring pattern, a portion of the ground wiringpattern on an opposite side from the heat-radiating member is exposed,and the member fitted into the cavity is a fastener for fastening theflexible circuit board and the heat-radiating member.
 8. The drivermodule structure according to claim 7, wherein the exposed portion ofthe ground wiring pattern and the fastener are connected via anelectrically conductive bonding material.
 9. The driver module structureaccording to claim 1, wherein the heat radiation agent is applied toinner sides of the accommodating portion.